Can we modify built-in object prototypes in JavaScript


Following is the code for modifying built-in object prototypes in JavaScript −

Example

 Live Demo

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
   .result {
      font-size: 20px;
      font-weight: 500;
      color: blueviolet;
   }
</style>
</head>
<body>
<h1>Modify built-in object prototypes</h1>
<div class="result"></div>
<br />
<button class="Btn">Click Here</button>
<h3>Click on the above button to call the alert method</h3>
<script>
   let resEle = document.querySelector(".result");
   let BtnEle = document.querySelector(".Btn");
   window.alert = function (msg) {
      resEle.innerHTML = "Custom Alert function has been triggered<br>";
      resEle.innerHTML += "Alert Message = " + msg;
   };
   BtnEle.addEventListener("click", () => {
      alert("Hello World");
   });
</script>
</body>
</html>

Output

On clicking the ‘Click Here’ button −

Updated on: 18-Jul-2020

113 Views

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